The National League MVP in 2013, McCutchen had been one of the game's true studs until he posted career lows in batting average (.256), on-base percentage (.336) and slugging percentage (.430) last year. His wRC+ of 106 was just slightly above league average, and after posting a Wins Above Replacement no lower than 4.9 every year since 2011, he went in the opposite direction in 2016, posting a -0.7 bWAR.

It was a really bad year at the plate, and also a horrible, no good, very bad year in the field as Pittsburgh's primary center fielder.

Among 54 qualified outfielders, McCutchen had the fewest Defensive Runs Saved (DRS) last year, with a whopping -28. His Ultimate Zone Rating (UZR), which calculates how many runs a player saved thanks to their range, was also worst in baseball, at -18.7. Here's a play from a game against the Marlins last August that helps tell the tale.

That wasn't even his best year in the DRS department, saving 24 in 2015 and another 20 in 2013, while also winning a Gold Glove in each of the last two seasons. His UZR has always been good and should increase dramatically in center, with more balls to go after, along with having to make longer runs to catch them.

Marte is an extremely talented defender, while McCutchen is declining in that area. Pittsburgh's outfield defense should improve with this move, which makes it a no-brainer.